Epidemiology of Baseball

A "Public Health Crisis" is defined as "Something so bad even an epidemiologist can find it." The other side of that coin is testing whether "Old Wives Tales" have any validity: does wearing your coat in cold whether protect against colds? Essentially this conflict is over which side has has to reject the null, and to what degree of confidence.

The same applies to sports and statistical analysis. While the subject may be trivial, fortunes are bet on game outcomes, and spent on athletes salaries in the hope of winning, based on these analyses.

The NYT sports page includes a column which somewhat misses the boat of the Bill James SABR paper "Underestimating the Fog," http://www.sabr.org/cmsfiles/underestimating.PDF

The James paper itself rejects the methods of proof of the following claims:

1. Clutch hitters don’t exist.
2. Pitchers have no ability to win, which is distinct from an ability to prevent runs.
3. Winning or losing close games is luck.
4. Catchers have little or no impact on a pitcher’s ERA.
5. A pitcher has little or no control over his hits/innings ratio, other than by striking batters out and allowing home runs.
6. Base running has no persistent impact on a team’s runs scored, other than by base stealing.
7. Batters have no individual tendency to hit well or hit poorly against left-handed pitching.
8. Batters don’t get hot and cold.
9. One hitter does not "protect" another in a hitting lineup.

These conclusions were reached by testing these hypotheses stated in the positive [clutch hitters exist] and failing to reject the null. Actually, the method seems something like comparing the ratio of a player's batting average with men on base in late innings to batting average generally in year 1, to the same statistic in year n. Conclusions were drawn by direct comparison of proportions, without use of confidence intervals or statistical tests. Bill James has shifted position, noting these claims are now indeterminate, not that they are wrong.



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http://www.nytimes.com/2005/04/24/sports/baseball/24score.html

Baseball's Leading Man of Math Has Some Second Thoughts About the Numbers

By DAVID LEONHARDT
Published: April 24, 2005